Sympathomimetics Flashcards
Mean Arterial Pressure Formula
CO x TPR
Cardiac Output Formula
SV x HR
Direct acting adrenergic agonists
Agonists for adrenergic receptors that can vary selectivity.
Indirect acting adrenergic agonist
Act away from adrenergic receptors and generally alter release of catecholamines from adrenergic neurons.
Mixed acting
Have direct and indirect agonistic effects.
Baroreceptor Reflex
Respond to increases or decreases in blood pressure by adjusting sympathetic or parasympathetic output.
Vasoconstriction
A1, A2 (minor),
Vasodilation
B2
Vascular Expression
Expressed in both arteries and veins, but primarily effects smaller arterioles and sphincters. Expression varies between vascular beds resulting in different responses to adrenergic stims.
Vascular expression skin, nasal mucosa, or splanchnic.
A1
Vascular Expression in Skeletal Muscle
B2 and A1
Receptors corresponding to the Heart
B1(predominant) B2(important in HF)
Activation leads to increased SA node activity, increased AV node conduction velocity, increased myocardial contractility, leading to increased CO.
Alpha 1 receptors are also expressed and increase contractility in a minor way
A1
Mydriasis, saliva increase, vasoconstriction(smooth and skeletal), GI relaxation, Bladder constriction, ejaculation
A2
Vasoconstriction of mucosa, saliva, skin, splanchnic.
B1
Renin secretion, increased fatty acid output, decreased GI motility.
B2
Increased ciliary aqueous humor, increased respiratory secretions, relaxation of bronchial smooth muscle, bladder relaxation, increased glucose output
Epinephrine
Agonist of both A and B receptors
Effects: Vasopressor, increased systolic pressure and decreased diastolic pressure, MAP unchanged(no baroreceptor reflex), increased HR, contractile force and CO, vasoconstriction, dilation of skeletal muscle vessels, decrease in TPR, bronchodilation, hyperglycemia, lipolysis.
Side Effects: Restlessness, headache, tremor, palpitations.
Cerebral hemorrhage(large or rapid doses), arrhythmia, angina(CAD).
Contraindications: Patients on Beta Blockers (unopposed activation of vascular A1 receptors resulting in severe HTN or cerebral hemorrhage).
Uses: Anaphylaxis, Bradyarrhythmias, asystole, mydriatic agent, glaucoma, co-administration with local anesthetic.
Norepinephrine
Same as Epi, but does not activate beta 2
Effects: Increase in both systolic and diastolic pressure(increase in MAP). Baroreceptor reflex response. Decreased HR, Increased contractile force, CO unchanged. Vasoconstriction and increased TPR.
Side Effects: Greater elevation in BP than Epi, Severe HTN, Necrosis at injection site, Peripheral vascular insufficiency.
Uses: Raise BP. Cardiogenic shock. Septic shock. Spinal anesthesia.
Dopamine
Low concentration is a D1 receptor agonist. High concentrations B1 and A1 agonist.
Low Dose: Vasodilation of renal, mesenteric, and coronary vasculature. Increases GFR and renal blood flow.
Intermediate Dose: B1 effects(HR up, Contractility up, Systolic up, Diastolic no effect)
High Dose: A1 effects(Vasoconstriction and TPR up).
Side Effects: Anxiety, headache, palpitations, angina pectoris, arrhythmias.
Uses: Decompensated Heart Failure, Cardiogenic Shock(NE preferred), Sepsis(NE preferred).
Isoproterenol
Potent nonselective Beta agonist with low affinity for alpha receptors.
Decrease diastolic pressure, systolic pressure unchanged or increased, MAP decrease. Increased HR, contractile force and CO. Decreased TPR. Bronchodilation.
Palpitations, Tachycardia, Headache, Flushing, Ischemia or arrhythmia.
Emergency stimulation of heart rate in patients with Brady or HB. Generally replaced by Epi and Dopamine.
Dobutamine
Non-selective B agonist
2 Isomers that are agonists of beta receptors
Minor BP effect, Increase contractility and CO. Minor effect of HR. Minimal effect on TPR.
Side Effects: Hypertensive patient’s may have an increase in HR or BP. A-Fib patients at risk of V-Tach due to increased AV conduction.
Uses: Cardiac Support CHF, After heart surgery, Acute MI.
B2 Selective Agonists
Selective of B2, but not absolute. Developed for Pulmonary use. Delivered via inhalation to target particularly pulmonary tissue.
Bronchodilation. Reduced Airway Inflamation.
Side Effects: Tremor, Anxiety, Tachycardia, Rare arrhythmias or ischemia. Reduced adverse effects due to inhalational administration.
Albuterol
Short Acting 3-6 hours. Bronchodilation in 15 mins. Used for Asthma, relief of bronchospasm.
Salmeterol and Formoterol
Longer Acting(>12 hours) B2 agonist
Salmeterol slow onset
Formoterol quick onset
Used for COPD and Persistent Asthma.
Mirabegron
B3 Selective Agonist
Bladder Relaxation
Side Effects: HTN, UTI, Headache.
Used for Urinary incontinence.
Phenylephrine and Midodrine
A1 selective agonists
Increases systolic and diastolic pressure, decreases HR, vasoconstriction.
Used for hypotension, nasal decongestant, as a mydriatic agent.
Ephedrine
Mixed Acting; Direct and Indirect, as it is an agonist for A and B receptors and enhances the release of NE from sympathetic neurons.
Effects: Increase BP, Increase HR and CO, Increases TPR, Increases resistance to urination, Bronchodilation, CNS stimulation.
Side Effects: HTN, Insomnia, adverse cardiovascular effects in people with underlying cardiovascular conditions.
Previously used to treat asthma. Dietary supplements were banned.
Pseudoephedrine
Similar to ephedrine, but is a direct A1 agonist and has little effect of B2 activity.
Use: Decongestant.
Cocaine
Indirect Sympathomimetic: Inhibits reuptake of NE and other neurotransmitters from synaptic cleft
Effects: Increased BP and HR
Side Effects: Arrhythmia, Ischemia, Myocarditis, Aortic Dissection, Cerebral Vasoconstriction.
Uses: Topical anesthetic of upper respiratory tract.
Amphetamine
Indirect acting sympatho
CNS stimulant with peripheral sympathomimetic actions. Releases neurotransmitters from vesicles in sympathetic nerve terminals.
Effects: Increases systolic and diastolic pressures, Slows HR, Contraction of urinary sphincter, Unpredictable GI effects, Strong CNS effects.
Uses: Narcolepsy, ADHD.
*Dextroamphetamine: Greater CNS and less peripheral action.
Methamphetamine
Indirect acting
Similar to amphetamine and ephedrine
More central stimulant effects with less peripheral sympathetic actions.
Methylphenidate
Piperdine derivative, structurally similar to amphetamine.
Mild CNS stimulant. More prominent effects on mental than motor.
Both methamphetamine and methylphenidate are approved for narcolepsy and ADHD.
